1. Field of the Invention
The present invention relates to object detection apparatus, in general, and to apparatus for sequentially detecting the presence of objects within a plurality of spaced-apart zones, in particular.
2. Description of the Prior Art
Apparatus incorporating acoustical or electromagnetic means for detecting distant objects are well known and understood in the prior art. Electromagnetic means such as radar, photoelectric devices and the like as well as acoustical devices utilizing ultrasonics have often been employed to detect remote objects or both detect such objects, and subsequently initiate some action or sequence of actions in response to their presence within a particular space or zone.
Ultrasonic and photoelectric intrusion alarm systems, such as those employed to protect personal property within a dwelling from unauthorized intruders, for example, are also well-known in the prior art. When such alarm systms are employed to detect the presence of an intruder within a plurality of separate or spaced-apart zones, present practice is to utilize a single energy-transmitting and receiving transducer, or a single set of energy-transmitting and receiving transducers for each space or zone wherein an intruder is sought to be detected. An example of a single energy-transmitting and receiving transducer incorporated in a mobility cane for the blind is shown in U.S. Pat. No. 4,280,204 to ELCHINGER. An example of a single set of energy transmitting and receiving transducers (one transducer for transmitting energy and the other for detecting an echo of same) incorporated in an automatically focusing camera, is shown in my U.S. Pat. No. 3,522,764.
Providing a plurality of transducers or transducer sets for each space or zone sought to be monitored or protected produces a number of disadvantages. Among these disadvantages are the increase in the amount of equipment necessary to construct an object detection or alarm system, the increased space required to locate and mount said additional equipment, the increased complexity of installing such a system and the increase in system equipment costs.